Cursor won't change shape depending on vi mode when running inside tmux

[AmdaU]

fish, version 3.4.0-62-g1763e7d3b
tmux 3.2a

EndevourOS
alacritty 0.11.0-dev (7312f33f)

The cursor always remains a block, no matter the vi mode when running fish inside of tmux.
I have tried running

sh -c 'env HOME=$(mktemp -d) fish'
fish_vi_key_bindings
set fish_cursor_default block
set fish_cursor_insert line
set fish_cursor_replace_one underscore
set fish_cursor_visual line

https://asciinema.org/a/EX9JCqHHpMbzbSCxed1BvnhGt

But no succes.

My tmux config is

set -s escape-time 0

unbind C-b
set-option -g prefix C-Space
bind-key C-Space send-prefix

The issue dosen't seem to be on tmux's side since changing cusor shape works in neovim.

Thanks!

[faho]

Vi cursor shaping isn't automatically enabled in tmux because it's impossible to detect when it supports it (when the outer terminal does).

So, inside tmux, you'll have to set $fish_vi_force_cursor to indicate you know better.

Do something like

if status is-interactive
    if string match -q -- 'tmux*' $TERM
        set -g fish_vi_force_cursor 1
    end
end

in config.fish.

[yochem]

Hi, I got the exact same problem, but in tmux v3.3a. I thought it was a problem on their side, but received this as response from a tmux maintainer: tmux/tmux#3226 (comment) (and see this comment for more explanation). I don't know much about escape sequences, but maybe this will be helpful?

P.S. the solution from @faho above did not work for me.

[faho]

Ah, lovely.

We do use the sequence they indicated to change the cursor, but we tell tmux to just pass it on. Apparently they disabled that and want to receive the sequence themselves. That's certainly possible.

However, unless tmux now interprets the sequence and determines if it is safe to hand it to the enclosing terminal, it's still not possible to actually enable the sequence by default in tmux (unless we detect the enclosing terminal, which in some cases, including alacritty, goes via $TERM, which tmux clobbers).

I've asked the tmux people for confirmation.

[faho]

The tmux people have confirmed we can pass on DECSCUSR (the xterm version) and don't have to do the passthrough dance anymore.

Reopening because we can now, in fact, handle tmux.

[yochem]

Sounds great. Thank you for the quick response and actions taken!

[zanchey]

DECSCUSR support appears to have been added in tmux 1.5 (2011), so I'm bravely taking this for 3.5.1.